Method of treating waste materials containing organic substances of animal or vegetable origin by mesophile or thermophile anaerobic conversion



2.198.737 ES OF ANIMAL April 30, 1940.

K. PETERSEN METHOD OF TREATING WASTE MATERIALS CONTAINING ORGANIC SUBSTANC OR VEGETABLE ORIGIN BY MESOPHILE 0R THERMOPHILE ANAEROBIC CONVERSION Filed June 25. 1938 I lave/71221: A a/ fi eirse/r XVQ I W A f/7s.

Patented Apr. 30, 1940 A DIESOPHILE OR 'IIIERMOPHILE ANAER- OBIC CONVERSION Kai Petersen, Buddlnge Vaerk, Soborg, near Copenhagen, Denmark Application June 25, 1938, Serial No. 215,932 In Denmark June 29, 1937 Claims. (Cl. 210-2) This invention relates to a method of treating waste materials containing organic substances of animal or vegetable origin by mesophile or thermophile anaerobic conversion.

5 It is known to convert waste materials, such as garbage and night soils, industrialrefuse. as well as waste materials from horticulture, agriculture and forestry into fertilizers or substances not causing hygienic difliculties and to purify 1o sewage and the like foul waste waters by means of biological processes. Hereby use has been made of the ability of the microorganisms occurring in nature to decompose the organic components of the materials mentioned; and accord- "ll. ingto'the employment of aerobic or anaerobic 'microorganisms'an aerobic or anaerobic conver-- sion or purification has been obtained, whereas the temperature at which the process takes place has been determining for whether the conversion or purification has been effected by means of mesophile or thermophile microorganisms.

The mesophile and thermophile anaerobic decomposition which has been used particularly in purifying waste waters is a fermentative and g5 putrefactive process taking place with formation of bad smell and a relatively large evolution of gases (methane, hydrogen sulphide, carbon dioxide, etc.) and beyond being of course dependent on thesubstances present the said decom- 0 position is, as is ,well-known highly dependent on the condition under which the decomposition takes place. When the decomposition is properly governed a gas can be obtained having an excellent calorific power, in some cases even higher than that of ordinary illuminating gas.

The present invention relates to a treatment of waste materials containing organic substances of animal or vegetable origin by mesophile or thermophile anaerobic conversion. As starting materials for the method according to the invention the more or less solid waste materials referred to above may be used, such as sewage sludge, garbage and night soil, packing house refuse, industrial refuse as well as waste materials from horticulture, agriculture and forestry or mixtures thereof; and the object .of the invention is then to obtain from a starting material in question a gas yield as large as possible and the smallest possible amount of sludge. The invention may also housed in purifying sewage and the like-foul waste waters in which case the gas yield and the remaining mass of sludge have 7 only secondary importance.

The invention also relates to an apparatus for carrylnfl out the anaerobic conversion.

position of the putrefactive substances may be interior of which there is no free access to at- PATENT OFFICE From the above mentioned anaerobic puriflcation of waste waters ordinarily taking place in septic tanks or Emscher wells it isknown to be connected with difllculties to start the proper fermentation and to maintain the said fermentation with formation of ,large amounts of gas. it is also known that acid-forming microorganisms may easily be predominating both when starting and during the operation whereby a vigorous foaming and reducted gas evolution occur, the intended development of the gas-forming putrefying'bacteria being retarded by the formation of acids. Such acid-forming fermentation will particularly occur in the presence of large carbohydrate contents and the said fermentation'may from an occasional place propagate through the whole mass. Even by the agitation hitherto used it has not been possible to completely secure the avoidance of an extending acid fermentation, since from nature's hand there are more than equal chances that an undesired acid fermentation will set in than that the ,inethane fermentation aimed at will be produced and maintained. Moreover, it has been practically difflcult to perform'heating during the conversion so'that at certain seasons a very slow and sometimes very small decomposition will be obtained.

The present invention provides a method and an apparatus by which, compared with hitherto known methods using a mesophile or thermophile anaerobic conversion, a highly increased capacity and an increased regulation and control of the course of the process are obtained whereby the conversion may be practicallycompletely governed and the most frequently objectionable secondary effects easily occurring in the known methods may be avoided. Moreover by means of the present invention a more complete decomobtained. Thereby, a higher gas yield and a smaller amount of sludge being at the same time morehighly putrefled are obtained.

The method according to the invention includes the step which comprises supplying the sludge to a rotary solid-walled container to the mospheric air; rotating the'said compartment to prevent sedimentation of any portion of the sludge and to provide agitation and intermixing of the whole sludge mass; and continuing the said mode of operation thereby effecting an anaerobic decomposition of the organic components of the sludge mass resulting in the evolution of combustible gases, the said agitation and i intermixing caused by the rotation of the said compartment facilitating the separation of the gases from the sludge particles and counteracting the appearance -of an acid-forming, foamproducing fermentation which may be detrimental to the gas-producing fermentation. Generally, it will be preferred to subject the material being treated to a turning over and intermixing in addition to the intermixing produced by the rotary movement of the container and to subject the material to grinding prior to or during or both prior to and during the anaerobic decomposition. However, how the method is carried out depends on the class of raw material in question. Therefore, other characteristic features of the method according to the invention together with the features of the apparatus. designed for carrying out the same will be stated in the following with-reference to the drawing diagrammatically illustrating various embodiments of an apparatus for carrying out the method according to the invention.

Figure 1 shows a vertical longitudinal sectional view of an embodiment of the apparatus according to the invention,

Figure 2 a similar sectional view of another embodiment and Figure 3 partly in section a further embodiment of the apparatus.

The apparatus shown in Figure 1 consists of a horizontally disposed solid-walled container H rotatably supported on rollers 29 andat its one end provided with a gear ring '25 meshing with a pinion 21. This pinion is operated by a power source not shown for-revolving the container. The said container is internally provided with blades 2! and contains grinding bodies 23, such as marble balls, iron balls, stone shippings,

inorganic waste materials or the like. By means of an airand water-tight connection I1 which may be of a construction known per se there are passed through the one end plate of the container both an inlet pipe l3 for the material to be treated which pipe terminates inside the container at the top (ceiling) thereof,,and an outlet pipe I5 for discharging the gas formed during the treatment. The pipe l5 may conveniently be connected with a gasometer not shown for collecting the gas. An outlet pipe IQ for the putrefied sludge and the accompanying liquid is passed through the other end bottom of the container. Also at this place an airand water-tight connection I1 is provided. The pipes l3, l5 and N! are provided with valves l4, l6 and I8, respectively.

The apparatus described above is particularly used in treating sludgy waste materials or waste materials, such'as night soil which may easily be converted into sludge during the rotating of the container by means of the grinding bodies 23.

When starting the apparatus the material to be treated, if desired, with addition of water and pH-controlling substances, such as lime is supplied to the container through the inlet pipe l3, the outlet pipe l9 being kept closed. It may be preferred to supply a suitable bacteria culture together with the material to be treated so that the biological conversion aimed at is quickly obtained. For this purpose the putrefied sludge from a previous conversion may, for instance, be used. When the container is filled the inlet pipe I3 is closed and the container is rotated by means of the pinion 21. The container is first rotated quickly so that an effective distribution of theinoculating material (eventually supplied) into the starting material and a quick and good disintegration and distribution of the latter are provided. When the anaerobic fermentation is well started the velocity of the container is somewhat reduced. The gas produced during the conversion flows through the outlet pipe l5 to a burner or a gasometer or another exploiting or collecting place for the gas. When the conversion is finished the velocity of the container is further reduced so that the container is rotated quite slowly m or completely stopped, if desired, in order to proinote sedimentation of the putrefledsludge residue. After resulting sedimentation the sludge and the accompanying liquid ,are discharged through the outlet pipe I 9. A suitable portion of u the putrefied sludge may be retained as inoculating material for new starting material. Instead of being discharged jointly the putrefied sludge and the accompanying liquid may be discharged separately, for instance by different adl) justments of the pipe 19.

If desired, the putrefied sludge may then be subjected to an aerobic after-treatment which may also be the case with the liquid discharged.

If desired, both may be after-treated jointly. 35

When the sludge is subjected to an aerobic after-treatment which may be considered most appropriate or when not it may in both cases be employed as a fertilizer.

Instead of carrying out the method discon- 30 tinuously as described above it may also be carried out continuously. For this purpose, however, the embodiments of the apparatus de-- scribed in the following are particularly suited.

By treating the raw material in the manner mentioned above a uniform conversion -will be obtained throughout the container, whereas conditions are provided that the conversion becomes so completely as possible, the rotation of the container and the simultaneous grinding providing a o uniform disintegration and 'distribution' of the material and a uniform distribution of the microorganisms. Thus, it is avoided that at some places of the container lumps of starting material are present and an accumulation ofthe sludge occurs. An acid fermentation is almost excluded and if such a fermentation should set in at local places of the container it will be quickly stifled due to the intensive agitation of the material.

If the starting material is not present in the 0 form of sludge or if the said material may not be easily converted into such form *by the grinding bodies eventually present in the container the material should be subjected to grinding prior .to or during the conversion- Grinding may be efu fected in a rotary chamber communicating with the compartment in which the anaerobic conversion substantially takes place, the said grinding chamber being preferably rotated at a velocity higher than that of the said compartment. The latter may be divided into two .chambers being operated at different velocities, the chamber nearest to the outlet end of the apparatus being operated at the lowest velocity, preferably a velocity being so low that a quick sedimentation 55 takes place. An apparatus of this construction is shownin Figure 2.

The grinding compartment 33, 35 is provided with a gear ring 38 connecting with a pinion 41 which is operated by a power source not shown. I0 'By means of an airand water-tight connection 49 the grinding compartment is connected with the compartments 46 and 56, respectively, in which the anaerobic conversion particularly takes place. Blades 2 I are provided in the com- 'terior bottom side of the container.

partment 46. As no agitation of the material is effected in the compartment 56 beyond the agitation produced byathe rotationof the container a. sedimentation ofthe putreii'ed sludge residue will here proceed to some extent. Therefore, 'at the outlet end of the container a separate. pipe 40 is provided for discharging the sludge, while the liquid is discharged through a pipe 44. v

The compartment 46 in which the main con-- version takes place is provided with a gear ring 48 meshing with a pinion 5| which is operated by.a

power source ,not shown and the almost completely converted material flows then into a compartment 56 where an after-conversion and sedimentation takeplace. The gas produced in the compartment 46 passes through a pipe 53 into the compartment 56 and is discharged through a pipe 39. Connection is provided between the compartment 46 and the compartment 56 in a manner known per se'by means of a pipe section 52 and an airand water-tight connection 54. The compartment 56 is provided with a gear ring and operated by a pinion 51 meshing there-' with.

The apparatus shown in Figures 1 and '2 may be modified in several respects without falling beyond the scope of the invention. Thus, the inlet and outlet pipes may all be arranged at one end of the container whereas the inlet pipe for the starting material may extend to the in- The container may also be provided with other agitating, devices than the blades shown in order to produce a more intensive agitation restricted to the upper layers of the liquid, if desired. The presence of grinding bodies is neither absolutely necessary in that it depends on the raw material in tion.

As the essential feature of the invention consists therein that the anaerobic conversion is wholly or substantially effected in a rotary, solidwalled container or drum it is to be understood that preand after-treatments being eventually necessary or suitable according, to the condition of the starting materials and the result aimed at and falling within the scope of the invention may be carried" out per se in any suitable manner. It is to be particularly pointed outthat, for instance, the invention is not restrictedto the provision of effecting a sedimentation or the sludge residue in a turnable container in that the sedimentation and a second putreiaction, ii dequessired, may be effected in one or more separate and stationary sedimentation containers.

If desired, such a stationary sedimentation container may be combined with a gasometer whereby a simple plant is obtained. An embodimentof such an apparatus diagrammatically in Figure 5. In this figure, I l designates in conformity with Figures 1 or 2 a rotatable container ordrum in which the whole or substantial part of the anaerobic conversion takes place and which is oper- 1 ated by a gear ring 25 ,and a pinion 21 whereas 60 is a gasometer the lower part 5| of which serves as sedimentation and after-putreiaction container. The gas produced in the container II is transferred to the gasometer thro h a pipe 62 and again removed from the said gasom'eter through a pipe and through a pipe provided with a valve 63 the sludge residue and the liquid remaining after the conversion are passed to the lower part SI of the gasometer'and at this place subjected to a sedimentation and also to an afterputreiaction, if desired. The putreiied sludge isshown G'Iwhile the liquid may be discharged through a pipe 66., j

The gas produced by the anaerobic conversion may be utilized as a poweror illuminating agent or for heating the material being treated in a manner known per se in that thestarting material may be heated prior to its entrance intothe container or the said container may be provided with'suitable heating devices, such as a heating jacket or internal heating pipes. However, the heating of the material may alsojbe provided in another way if a thermophile conversion be desired.

In the same way, the anaerobic conversion may be mesophile or thermophile or the method may a portion of purified sludge residue is returned to the apparatus in a manner known per se.

In the above description and in the following patent claims the expression anaerobic conversion is employed in accordance with the common terminology, but as it cannot be said to be scientifically proved that the methane-producing microbes are working absolutely anaerobic the supposition to the contrary being recently advanced from diflerent sides that the methane fermentation is produced by micro-aerophile microbes it will be understood that the expression referred to above must be interpreted with some discretion and that it also falls within the scope of the invention to adopt measures for supplying oxygen or other controlling media (in a. gaseous, liquid or solid state) to the conversion container and for controlling the pressure therein, if desired. In view of the suppositionreferred to it may be tapped oil? at the bottom through a cock may namely be appropriate at a certain operating taining a well suited specific pressure upon the material being putrefl'ed so that increased control of the putrefying velocity and the proportion of sludge residue to gas yield are obtained. As already mentioned above it may be appropriate to use means for supplying. pH-controlling agents to the conversion container, for instance lime. I

If desired, also suitable hutriments to the microorganisms the developments of which it is other organic waste materials in slurry condition by means of anaerobic gas-producing fermentation, the step which comprises supplying the sludge to a rotary solid-walled container to the interior of: which there is no free access to atmospheric air; rotating the said compartment to prevent sedimentation of any portion of the sludge and to provide agitation and inter-mixing of the whole sludge mass; and continuing the said mode of operation thereby eflecting, an anaerobic decomposition of the organic components of the sludge mass resulting in the evolution of combustible gases, the said agitation and intermixing caused by the rotation of the said compartment facilitating the separation of the gases from the sludge particles and counteractlog thevappearance of an acid-forming, foam- 1 genizing action produced by' the rotation of the said compartment and keeping the interiorwalls of the same clean by rubbing off the sludge particles adhering thereto.

3. Method as claimed in claim 1 which comprises reducing the speed of rotation of the rotary compartment to allow sedimentation of the sludge particles when the major portion of ,the anaerobic fermentation has taken place and separately removing the clarified liquid and the settled sludge residue from the said: compartment.

4. Method as claimed in claim 1, which comprises transferringthe sludge from the rotary compartment to a stationary compartment when the major portion of the anaerobic fermentation has taken place, allowing a sedimentation to occur in the said stationary compartment and separately removing the clarified liquid and the settled sludge residue therefrom.

5; In an apparatus for treating sewage sludge and other organic waste materials in slurry condition by means of anaerobic gas-producing fermentation the combination of arotary solidwalled container being substantially horizontally disposed and to the interior of which there is no free access to atmospheric air, two end plates closing the opposite ends of the said container, means for rotating the container, a pipe for supplying the sludge to be treated, a pipe for discharging the fermented sludge residue and a pipe for discharging the gases formed during the fermentation, said pipes extending axially through the said end plates and being airand watertightly connected therewith.

KAI PETERSEN. 

